TBR Antigens Clarification

[justadream]

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TBR Bio says that
“Before a person is exposed to an antigen, there are no antibodies for that particular antigen”

But how would clonal selection work if there wasn't a single antibody for the antigen? I thought there had to be at least 1 initial antibody that binds to an antigen. After than initial binding, that chosen antibody will proliferate.

 

[Czarcasm]

TBR Bio says that
“Before a person is exposed to an antigen, there are no antibodies for that particular antigen”

But how would clonal selection work if there wasn't a single antibody for the antigen? I thought there had to be at least 1 initial antibody that binds to an antigen. After than initial binding, that chosen antibody will proliferate.

For clonal selection of naive B cells to occur, the antigen must be digested and presented by an APC (Dendritic Cell, Macrophage, B-Cell); Each of these cells digest the antigen and present it on an MHC II. The MHC II with it's antigen can activate CD4/CD8+ T Cells. Of particular interest here, is the activation of CD4 T cells to T helper cells. Here the antigen-MHC II binds to CD4 co-Receptor (on T cell), and the antigen itself stimulates the TCR (T Cell Receptor); this causes clonal expansion of that particular naive T cell (which becomes activated to a mature T cell). This mature T cell then facilitates the process of antibody production by locating a naive B cell which can recognize an epitope of the same antigen; the naive B cell BCR, upon binding to the epitope will be activated and undergo clonal selection to produce memory cells and (activate) plasma cells (the antibody secreting cells) of the immune system.

In short, antibodies must be produced by a plasma cell first before they exist in plasma. The only way for this to occur is if it's associated B cell was activated (underwent clonal expansion and activation). Otherwise, no antibodies would exist in solution. (The only exception here is of course, pre-made plasma containing antibodies were injected into an individual).